In the binary system IPHAS J190812.63+045728.1, every five hours one star completely covers the other. For 18 minutes, the white dwarf and its gas disk disappear, leaving only the red companion visible. It is as if a bright spotlight on stage were switched off, and the audience finally saw the modest actor who had been standing there all along. Astronomers used this moment to measure the donor star without interference.

Previously, the parameters of the donor in such systems had to be inferred from indirect clues, because the disk overwhelmed its light. Here, the orbit is edge-on, and every 5.073 hours the companion passes directly in front of the white dwarf. The spectrum revealed a star of spectral class M2.3 with a mass of about 0.50 solar masses and a radius of 0.55 solar radii. It is an ordinary red dwarf, but seen directly. The X-ray telescope XMM-Newton added a puzzle: the emission is hard, which usually indicates a magnetic white dwarf, but over seven years the system erupted every 60 days, like a dwarf nova. The two scenarios do not add up, which gives scientists a rare test for models. When the shutter opens again, the white dwarf will return to the stage, but now we know who feeds it.